JPS6038460B2 - High carbon ferrochrome granulation shot and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high carbon ferrochrome granulated shot and a method for producing the same.

Demand for high-carbon ferrochrome shot products has recently increased.

The features of this shot product are that it is easy to handle and is inexpensive. On the other hand, its drawbacks are that it contains many fine particles, and because it is lightweight, it is difficult to enter the target molten metal (for example, stainless steel). Conventional high-carbon ferrochrome shot products are produced using the granulation shot method, in which high-pressure fluid is sprayed from an injection nozzle into the melt flow flowing down from a ladle to disperse the molten metal, and at the same time, the molten metal is dropped into a water tank to granulate it. It is produced by two methods: pouring it into a mold and solidifying it, then crushing it into an appropriate size to form a lump.

Among these manufacturing methods, the latter mold solidification method has problems such as difficulty in crushing and the production of many particles of poor particle size. The former water crushing method does not require crushing and is easier than the mold solidification method, but it has the following disadvantages. In other words, the shot obtained by the conventional water pulverization method exhibits a shell-like, rough-faced, flat-sided, square-shaped geometric grain shape (see the photograph in Figure 1) and is therefore extremely tall. exhibits a green hue. Furthermore, the size of most of the shots is 3 to 12 skin, and the high specific gravity of the shot never exceeds 3.0. In this way, because it exhibits the geometric grain shape of the square surface, it is easy to generate fine particles during transportation and handling, and because it has a small specific gravity and is bulky, it is easy to powder. When used, there are problems with yield and handling, and furthermore, when added to molten metal or slag, it has various drawbacks such as easy floating. The reality is that granulated shot has not been widely adopted due to these drawbacks. This invention was developed with the intention of providing a granulated shot of high carbon ferrochrome that improves the drawbacks of the granulated shot, and a method for producing the same.

The high carbon ferrochrome granulated shot of the present invention has the following characteristics. A granular material with a packed bulk specific gravity of 3.40 or more, a smooth metallic luster on the surface, and a rounded polygonal geometric grain shape (see the photo in Figure 2).
This is a granulated water shot made up of the majority (90% or more) of size 5.

The composition of high carbon ferrochrome is as follows.

Cr: 55-70%, C: 6-8.5%, Si: 1.5
~8%, P: <0.04%, S: 0.05-0.08%
, Son: Fe This high carbon ferrochrome shot is manufactured as follows.

It is obtained by adding aluminum or an aluminum alloy or a calcium-silicon alloy to a high-carbon ferrochrome molten metal and pulverizing it.

As aluminum alloys, Fe-AI, Fe-Yamaichi Si
For example, AI>50% or more is desirable, and as Ca-Si, Ca25% or more is suitable. The form of each of the above additives may be in any form such as granule, powder, or fragments, but in consideration of solubility and reactivity, 3.
For fragments, pieces with a thickness of less than 1 piece are used. The additive may be added to the molten metal by placing it on the bottom of the ladle or adding it to the ladle while it is being damaged.

In any addition, it is necessary to mix the additives thoroughly by falling convection of the molten metal. The amount of the additive added is preferably about 0.01 to 0.5 skin t% as AI or Ca based on the high carbon ferrochrome molten metal.

When the silicon content in the water granulated shot increases beyond a certain amount without adding the above-mentioned AI, etc., the grain shape becomes fan-flat and has many sharp edges, and the grain surface becomes dull and rough with a greenish color. If the silicon content is lowered, grains with a somewhat rounded polygonal grain shape and smooth grain surfaces with a metallic luster can be obtained.

In this case, it has been confirmed by the experimental results of the present inventors that grains with a slightly rounded grain shape and a metallic luster tend to be preserved. cannot generally be determined based on silicon content. This means that although the silicon content in the granulated water shot is higher than that contained in the conventional granulated water shot, as shown in Example 1, which will be described later, the granulated water shot of the present invention should have the following. satisfies the elements. This is considered to be based on the result that the main component of the additive has some effect. In the method for producing granulated shot of this invention, first, high-carbon ferrochrome molten metal tapped from a smelting furnace is received in a ladle.

At this time, additives are added as described above. Next, the falling sun is allowed to fall from the ladle tilting stand through the tundish into the aquarium at a predetermined rate (2 to 3 ton'min), and at the same time, a high-pressure fluid (e.g. water, It is obtained by ejecting water (steam, air) to blow away the falling molten metal, causing it to fall into a water tank. The water pressure is about 1 to 10k9' of the same as that used for conventional water fracking shots. Other operating conditions, such as the flow rate of the high-pressure fluid to be ejected and the water temperature in the water tank, are determined by taking into consideration the temperature of the molten metal and its components, as in the secondary water fracking method. Next, the present invention will be specifically explained with reference to Examples.

Example 1 High carbon ferrochrome Rakuyo tapped from an electric smelting furnace (
The hot water (temperature of about 1600°C) is received in a ladle (capacity 2, etc. n).

Place 25k9 pieces of aluminum (N: 99%, size approximately 10-20 pieces) on the bottom of the ladle in advance.
When about 1 cup of molten metal had been deposited, another 15k9 piece of aluminum was dropped.

At the same time as the aluminum pieces were melted, they were uniformly mixed by the condensation movement caused by the falling force of the port hot water (the head at the time of receiving the hot water was 2.5, and the head at the final time was 0.7). In addition, as a comparative example, the above-mentioned port hot water was poured into a separate ladle using a kiriboshi sardine pipe without adding any aluminum pieces.

The molten metals in the ladles of the present example and the comparative example were crushed under the same conditions to obtain shots.

The results are shown in the following table (Table-1).

Table 1 As shown in the above table, the granulated shot according to the present invention has many smooth surfaces, so there is less surface oxidation film, and the increased filling density and smooth surface cause less pulverization during handling, such as When added for adjustment in stainless steel manufacturing,
Since there are no harmful effects such as floating on the slag surface, it can be an excellent product in terms of crawling.

Furthermore, the bulk specific gravity of the shot single particles also increases from 5.8 to 5.9 to 6.40 to 6.55 by adding aluminum. This fact indicates that the fineness of the shot grains is improved. Therefore, when used, conventional products tended to float on the slag surface and had the disadvantage of lowering the yield, but this drawback has been improved. Furthermore, as shown in Table 1, the particle size distribution of the shot is 53.2% for the comparative product, while the product of the present invention has a uniform particle size of 84.0%. In contrast to 12.5% of the comparative example product, the product of the present invention had a very small amount of powder having 3 or less ribs at 0.2%. Example 2 Calcium silicon alloy (composition: 25% Ca, 55% Si, remainder mainly Fe) 240k9 was pulverized into the high carbon ferrochrome molten metal of Example 1 in the same manner as in Example 1 to produce shot.

The results were as shown in Table-2. Table 12 Reference Example In a steelmaking induction furnace with a capacity of 2 bn, stainless steel was manufactured using the products of the present invention shown in Table 11 in a 6-charge operation. The chromium yield and power consumption were improved as shown below.

Table-3 Operation results table (per lton of steel tapped)

[Brief explanation of drawings]

Figure 1 is a photograph of a shot obtained using the conventional water fracturing method;
The figure is a photograph of the water granulation shot of the present invention. key mist key

Claims (1)

[Scope of Claims] 1. Granulated high carbon ferrochrome which is a granular material having a packed bulk specific gravity of 3.40 or more, a smooth surface, a metallic surface, and a rounded polygonal geometric particle shape. shot. 2 Adding and melting aluminum or an aluminum alloy or a calcium-silicon alloy to a high carbon ferrochrome molten metal, and pulverizing the molten metal. Filled bulk specific gravity is 3.40 or more, the surface is smooth and has no metallic luster. , a method for producing high carbon ferrochrome granulated shot, which is a granule having a rounded polygonal geometric particle shape.